In the automatic data identification industry, the use of RFID transponders (also known as RFID tags) has grown in prominence as a way to track data regarding an object on which an RFID transponder is affixed. An RFID transponder generally includes a semiconductor memory in which information may be stored. An RFID interrogator containing a transmitter-receiver unit is used to query an RFID transponder that may be at a distance from the interrogator. The RFID transponder detects the interrogating signal and transmits a response signal containing encoded data back to the interrogator. RFID systems are used in applications such as inventory management, security access, personnel identification, factory automation, automotive toll debiting, and vehicle identification, to name just a few.
Such RFID systems provide certain advantages over conventional optical indicia recognition systems (e.g., bar code symbols). For example, the RFID transponders may have a memory capacity of several kilobytes or more, which is substantially greater than the maximum amount of data that may be contained in a bar code symbol. The RFID transponder memory may be re-written with new or additional data, which would not be possible with a printed bar code symbol. Moreover, RFID transponders may be readable at a distance without requiring a direct line-of-sight view by the interrogator, unlike bar code symbols that must be within a direct line-of-sight and which may be entirely unreadable if the symbol is obscured or damaged. An additional advantage of RFID systems is that several RFID transponders may be read by the interrogator at one time.
An RFID transponder may be provided by an integrated circuit package affixed or coupled to a flexible substrate. Such flexible substrates may be efficiently manufactured using tape or film in a reel-to-reel packaging process. As shown in FIGS. 1A and 1B, the substrates 110 of such RF transponders 100 are typically rectangular in area having a length ("L") and a width ("W") wherein the length is greater than the width (L&gt;W). In conventional reel-to-reel RFID transponder packaging processes 200, illustrated in FIGS. 2A, 2B, and 2C, RFID transponders 100 are formed transversely on the tape 210 (e.g., so that their length ("L") is aligned with the width ("x" direction) of the tape 210 while their width ("W") is aligned with the length ("y" direction) of the tape 210).
This conventional process 200 has several shortcomings. First, the tape 210 cannot accommodate a transponder 100 having a substrate 110 with a length ("L") longer than the workable width of the tape ("G"). Thus, the workable width of the tape ("G") limits the length of antenna circuits 112 formed on the substrate 110 of the RFID transponders 100. For example, RFID transponders 100 may be manufactured using tape 210 comprised of a polyimide film 212 having sprocket holes 214 formed along both edges 216 and 218. Such film 212 is typically manufactured in several standard widths of which the most common, and hence the most inexpensive, is thirty-five millimeter (35 mm). Consequently, utilizing the conventional process 200, larger films (e.g., seventy (70) mm, one hundred twenty (120) mm, etc.) must be utilized to manufacture RFID transponders 100 having lengths ("L") greater than the workable width ("G") of 35 mm film or tape (approximately twenty-nine (29) mm) at a correspondingly higher cost.
Further, wherein the length ("L") of the substrate 110 is less than the workable width of the tape (L&lt;G), some areas near the edges 216 and 218 of the tape 210 are unused and wasted. Similarly, wherein the length of the substrate 110 is much less than the workable width of the tape (L&lt;&lt;G), large areas near the edges 216 and 218 of the tape 210 are wasted. Thus, as shown in FIG. 2C, wherein a wider film (e.g., 70 mm, 120 mm, etc.) is used in manufacturing the RFID transponders 100 having lengths ("L") of, for example, fifty (50) to fifty-five (55) mm, a large portion of the film 212 is wasted. Finally, the width ("W") of the substrate 110 is often of similar size to the sprocket hole pitch ("F") of the tape 210. Thus, the quantization error (i.e., the tape area wasted due to tape indexing by the sprocket holes 214) is usually very large in terms of the percentage of the actual transponder area. In order to reduce the quantization error, and thus improve the efficiency of the process, the design (and often the performance) of the RFID transponder 100 must be compromised.
As a result, it would be advantageous to provide improved methods and apparatus for manufacturing radio frequency transponders having flexible tape substrates wherein the length of the transponder is not limited by the workable width of the tape substrate.